Systems and methods for imaging plural axial locations

ABSTRACT

An imaging system is provided including a gantry, a bed, nuclear medicine (NM) imaging detectors, and a processing unit. The NM imaging detectors are disposed about the bore of the gantry. The processing unit is operably coupled to the imaging detectors, and is configured to acquire first NM imaging information of the object with the imaging detectors in a first axial position, iteratively actuate the gantry in a series of steps between the first axial position and the second axial position, acquire additional NM imaging information of the object at each of the steps, and reconstruct an image of the object using the first NM imaging information and the additional NM imaging information.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates generally to apparatus andmethods for diagnostic medical imaging, such as Nuclear Medicine (NM)imaging.

In NM imaging, systems with multiple detectors or detector heads may beused to image a subject, such as to scan a region of interest. Forexample, the detectors may be positioned adjacent the subject to acquireNM data, which may be used to generate a planar (2D) or athree-dimensional (3D) image of the subject.

NM imaging systems systems may have moving detector heads, such as gammadetectors positioned to focus on a region of interest. For example, anumber of gamma detectors may be moved (e.g., rotated) to differentangular and/or rotational positions for acquiring image data.

However, such detector heads may have a relatively small field of viewalong an axial direction, for example. Thus, to image larger portions ofthe body, or to image organs that do not completely fall within thefield of view, it may be necessary to acquire a series of images atdifferent times. However, for dynamic studies, images acquired atdifferent times may not be as clinically useful as desired.

Other nuclear cameras, such as the General Electric Discovery NM 530c(http://www3.gehealthcare.com/en/products/categories/nuclear_medicine/cardiac_cameras/discovery_nm_530c),for example, may be based on multiple pinhole configurations, and mayalso have a limited axial Field Of View (FOV). For example, a nuclearcamera that is optimized for cardiac imaging may have a limited FOV inall 3 dimensions, and may be capable of rapidly acquiring a 3D image ofthe limited-sized FOV. It may be noted that a multi-pinhole based cameramay not require motion (e.g., rotation) of a gantry or supportstructure, and/or of detector units relative to each other, to acquire asingle-photon emission computed tomography (SPECT) image. However, someof these cameras may perform a limited motion during SPECT acquisitionto acquire data from more view-points with respect to the target tissue.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, an imaging system is provided including a gantryhaving a bore therethrough, a bed, plural nuclear medicine (NM) imagingdetectors, and a processing unit. The bed is translatable between afirst axial position and a second axial position along an axis of thebore of the rotating gantry, and is configured to support an object tobe imaged. The NM imaging detectors are disposed about the bore of thegantry. The NM imaging detectors define an axial field of view and anin-plane field of view. The processing unit is operably coupled to theimaging detectors, and is configured (e.g., programmed) to acquire firstNM imaging information of the object from the imaging detectors with theimaging detectors in the first axial position; iteratively actuate thegantry in a series of steps between the first axial position and thesecond axial position; acquire additional NM imaging information of theobject at each of the steps; and reconstruct an image of the objectusing the first NM imaging information and the additional NM imaginginformation, wherein the image corresponds to an axial field of viewthat is larger than the axial field of view of the imaging detectors.

In another embodiment, a method for imaging is provided. The methodincludes acquiring first nuclear medicine (NM) imaging information of anobject to be imaged with plural NM imaging detectors at a first axialposition. The imaging detectors are disposed about a gantry having abore therethrough, with the object disposed on a bed translatable alongan axis of the bore between the first axial position and a second axialposition. The imaging detectors have an axial field of view. The methodalso includes iteratively actuating the gantry in a series of stepsbetween the first axial position and the second axial position, as wellas acquiring additional NM imaging information of the object at each ofthe steps. Further, the method includes reconstructing an image of theobject using the first NM imaging information and the additional NMimaging information, wherein the image corresponds to an axial field ofview that is larger than the axial field of view of the imagingdetectors.

In another embodiment, an imaging system is provided that includes afirst gantry having a bore therethrough, a second gantry axially alignedwith the first gantry and configured to be translatable axially relativeto the first gantry, a bed that is translatable along an axis of thebore of the first gantry, plural nuclear medicine (NM) imaging detectorsdisposed about the bore of the first gantry and the second gantry, theimaging detectors having an axial field of view; and a processing unitoperably coupled to the imaging detectors. The processing unit isconfigured to axially translate the bed and the second gantry withrespect to the first gantry to position the first gantry about a firstregion of interest and to position the second gantry about a secondregion of interest; acquire, concurrently, NM imaging information fromthe imaging detectors of the first region of interest and the secondregion of interest; and reconstruct an image using the NM imaginginformation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an imaging system in accordance with anembodiment.

FIG. 2 is a schematic view of the gantry and detectors of the imagingsystem of FIG. 1 at a first rotational position.

FIG. 3 is a schematic view of the gantry and detectors of the imagingsystem of FIG. 1 at a second rotational position.

FIG. 4 is a schematic view of the gantry and detectors of the imagingsystem of FIG. 1 at a third rotational position.

FIG. 5 is a graph corresponding to a sinusoidal movement of a bedrelative to a gantry in accordance with various embodiments.

FIG. 6 depicts varying coverage of portions of a FOV in accordance withvarious embodiments.

FIG. 7 is a perspective view of imaging systems in accordance withvarious embodiments.

FIG. 8 is a schematic view of an imaging system with two gantries inaccordance with various embodiments.

FIG. 9 is a flowchart of a method in accordance with variousembodiments.

FIG. 10 is a schematic block diagram of a Nuclear Medicine (NM) imagingsystem in accordance with an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of certain embodiments will be betterunderstood when read in conjunction with the appended drawings. To theextent that the figures illustrate diagrams of the functional blocks ofvarious embodiments, the functional blocks are not necessarilyindicative of the division between hardware circuitry. For example, oneor more of the functional blocks (e.g., processors or memories) may beimplemented in a single piece of hardware (e.g., a general purposesignal processor or a block of random access memory, hard disk, or thelike) or multiple pieces of hardware. Similarly, the programs may bestand alone programs, may be incorporated as subroutines in an operatingsystem, may be functions in an installed software package, and the like.It should be understood that the various embodiments are not limited tothe arrangements and instrumentality shown in the drawings.

As used herein, the terms “system,” “unit,” or “module” may include ahardware and/or software system that operates to perform one or morefunctions. For example, a module, unit, or system may include a computerprocessor, controller, or other logic-based device that performsoperations based on instructions stored on a tangible and non-transitorycomputer readable storage medium, such as a computer memory.Alternatively, a module, unit, or system may include a hard-wired devicethat performs operations based on hard-wired logic of the device.Various modules or units shown in the attached figures may represent thehardware that operates based on software or hardwired instructions, thesoftware that directs hardware to perform the operations, or acombination thereof.

“Systems,” “units,” or “modules” may include or represent hardware andassociated instructions (e.g., software stored on a tangible andnon-transitory computer readable storage medium, such as a computer harddrive, ROM, RAM, or the like) that perform one or more operationsdescribed herein. The hardware may include electronic circuits thatinclude and/or are connected to one or more logic-based devices, such asmicroprocessors, processors, controllers, or the like. These devices maybe off-the-shelf devices that are appropriately programmed or instructedto perform operations described herein from the instructions describedabove. Additionally or alternatively, one or more of these devices maybe hard-wired with logic circuits to perform these operations.

As used herein, an element or step recited in the singular and precededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features. Moreover, unless explicitlystated to the contrary, embodiments “comprising” or “having” an elementor a plurality of elements having a particular property may includeadditional elements not having that property.

Various embodiments provide systems and methods for nuclear medicine(NM) imaging. Generally, a radiopharmaceutical may be introduced into anobject to be imaged (e.g., via injection into a human or animalpatient), and used for imaging, for example a portion of an object suchas one or more organs of interest. NM imaging may be useful, forexample, in conjunction with functional studies of one or more organs ofinterest. Various embodiments provide for dynamic imaging of a region ofinterest (ROI) that is larger than a field of view of one or more gammacameras or other detectors used to acquire imaging information for thedynamic imaging. Dynamic imaging of a ROI larger than the field of viewof the camera(s) or detector(s) may be useful, for example, for dynamicrenal studies, for which both the kidneys and bladder are to be imaged,or, as another example, for patients whose kidneys are not at the samerelative height in the pelvis (for example, due to a kidney transplant).As one more example, dynamic studies of the lungs or other organs mayrequire imaging of a ROI that is larger than a field of view of a cameraor detector.

In various embodiments, during performance of a single imaging scan(e.g., collection or acquisition of information processed as a group toprovide one or more images, in contrast to a series of different imagingscans for which information is not processed as a group), a bedsupporting an object to be imaged may be repeatedly or iteratively movedbetween at least two axial positions, thereby providing imaginginformation over a greater range than an axial field of view (FOV) ofdetectors of a system. For example, a camera (or cameras) may be used tosequentially image two axial FOV's for a dynamic scan of two (or more)organs that are located too far apart to be covered by the axial FOV ofthe camera, or, as another example, for a dynamic scan of a region ofinterest that is larger than the axial FOV of the camera. In someembodiments, a bed supporting a patient for a dynamic renal study may betranslated back and forth during the study to intermittently collectimaging information of the kidneys and bladder (in contrast tocollecting all imagining information for use for the kidneys over afirst duration and all imaging information for use with the bladder overa second duration that does not overlap with the first duration).

The back and forth motion of the bed may be generally continuous in someembodiments, and may be performed as a series of discrete steps in otherembodiments. Further, it may be noted that the FOV's or correspondingaxial positions may be contiguous, separated, or overlap in variousembodiments. Further still, more than two FOV's or ranges may beemployed, with the FOV's or ranges contiguous, separate (or discrete),or a combination of contiguous and separate (e.g., some rangescontiguous and some ranges discrete). In some embodiments, the rangesmay be covered in a cyclic fashion, with the duration of each cycle (ortime spent at a given axial position before starting a new cycle at adifferent axial position) being shorter than a time required for orcorresponding to a dynamic process being studied (e.g., time requiredfor upload and/or washout). Further, in various embodiments, one or moreimages may be corrected or adjusted to account for isotope lifetime.

In some embodiments, instead of using only a single gantry (or ring uponwhich detectors are positioned), two or more gantries or detector ringsmay be used in tandem. For example, if each gantry or ring has an axialFOV of about 20 centimeters, two gantries or rings used in tandem mayprovide an axial FOV of about 40 centimeters. Further, at least one ofthe gantries or rings may be axially adjustable with respect to anothergantry or ring to provide for simultaneous or concurrent imaging in twodifferent axial positions. Instead of cycling back and forth between twoFOV's, imaging information for both FOV's may be acquired at the sametime. Optionally, each gantry or ring may have columns, with each columnhaving a smaller FOV than the entire gantry or ring.

Various scanning strategies (e.g., strategies for moving detectorsrotationally about a gantry and axially along a bore of the gantryrelative to an object being imaged) may be employed for overlappingFOVs, adjacent or contiguous FOVs (or FOVs sharing a common border), ornon-contiguous FOVs (or FOVs spaced apart or not sharing a common borderor overlapping). For example, for overlapping FOVs, if two or moreorgans of interest (or ROIs) are close enough that the two or moreorgans of interest may be viewed without shifting a camera the width ofone full FOV, the bed supporting a patient may be axially translatedback and forth less than a full FOV. For example, the bed may be axiallytranslated only enough so that the entire region of interest is covered.

As another example, for non-contiguous FOVs, if two or more organs ofinterest (or ROIs) are situated far enough apart such that the two ormore organs may not be seen by shifting a camera view the width of onefull FOV or less, the bed may be axially translated between two separateFOVs, with an intermediate zone between the FOVs not imaged.

In some embodiments, the bed may be axially translated in a sinusoidalor otherwise periodic and generally continuous fashion. A bed may beunderstood as being axially translated in a generally continuous fashionwhen the motion between two endpoints of travel is continuous. Forexample, the bed may pause momentarily at an endpoint to transition frommotion in one direction to motion in an opposite direction while stillbeing translated generally continuously as used herein. In someembodiments, during acquisition of imaging information (e.g., during allor a portion of an acquisition period), the bed may be translated backand forth in an undulating or oscillating motion. By using a generallycontinuous motion, the acceleration or jarring associated with stoppingand starting of the bed at numerous axial steps may be reduced, therebyreducing patient motion and discomfort.

It may be noted that, while 3-dimensional imaging (e.g., single photoncomputed tomography (SPECT)) may provide more detailed or completeimages than planar imaging, planar imaging may provide sufficient enoughimage quality for use in dynamic studies. Accordingly, planar imagingmay be utilized in various embodiments. For example, a sequence ofactuations performed during acquisition of imaging information as partof a scan may be as follows: First, with the bed being translated in afirst direction axially through the bore, imaging information isacquired with the detectors stationary at a single rotational position.Then, when the bed reaches the end of travel in the first direction, andis reversing course to travel in a second direction opposite of thefirst direction, the detectors may be rotated (e.g., rotated such thatthe detectors move the width of a detector head or detector field ofview) to a new rotational position. The bed may then be translated inthe second direction axially through the bore, with imaging informationacquired with the detectors until the time when the bed reaches the endof travel in the second direction. While the bed switches directions,the detectors may again be rotated (e.g., rotated such that thedetectors once again move the width of a detector head or a detectorfield of view). The back and forth motion of the bed along with therotation at the end positions of the bed may be repeated until a desiredamount of imaging information has been acquired.

In various embodiments, focused imaging may be used to enhance dynamicimaging. For example, a dynamic portion of a study may be performedusing planar imaging (e.g., detector heads not rotating with respect toeach other) to save acquisition time during a dynamic portion of astudy. Further, attenuation correction may be applied using SPECTinformation acquired before or after the dynamic portion, or using CTinformation acquired before or after the dynamic portion (for example,to help distinguish the organ of interest from interfering tissue). Asanother example, a lower dose or different type of isotope may be usedfor locating a target organ (or organs) of interest before a dynamicacquisition.

In some embodiments, stationary detectors may be aimed at an organ (ororgans of interest). The resulting image may be of relatively lowquality due to a relatively low number of views, but may be correctedwith subsequently acquired SPECT information (e.g., information acquiredwith a larger number of views per detector). For example, a first pass(or group of passes) may be performed with stationary or non-pivotingdetectors (it may be noted that a “stationary” detector may rotate witha gantry), and then imaging in a second pass (or group of passes) usingSPECT over a region of interest. In some embodiments, a later pass (orgroup of passes) may be taken over an entire transaxial volume includingthe region of interest.

In some embodiments, detectors may be focused on a target organ (ororgans) during a fast changing part of an acquisition, and used to imagethe remainder of a FOV during slowly varying times. Further, a greaterpercentage of imaging time may be spent with detectors focused on atarget organ (or organs) than on non-target portions of one or moreFOV's.

In various embodiments, a panoramic image may be created from each sweepor rotation of a detector head. Such an image may provide a somewhatdistorted version of a frame acquired using a parallel hole collimator.However, the information may still be useful. For example, the panoramicimage may be displayed with a corresponding forward projection image(e.g., an image derived using CT information acquired using a similarprocedure as the emission or NM projections)). Further, an additionalforward projection of CT information at an “undistorted” view may beprovided, for example a projection of CT information corresponding to aview angle at the middle or center of the sweep of the detector head.

Various embodiments may be employed with different imaging protocols.For example, in connection with multi-gating imaging (MUGA), some partsof a fast changing organ may be imaged using planar imaging, and/or withstationary or non-pivoting detectors. As another example, a first passof a cardiac imaging protocol may be performed stationary ornon-pivoting detectors, with subsequent SPECT imaging. As one moreexample, in a renal imaging protocol for imaging the kidneys and bladdermay be axially displaced from each other. The axial position of apatient with a bed may be controlled to alternate between two or moreFOV's for interleaved or intermittent imaging of the axially displacedROI's. Further example protocols that may be performed using one or moreaspects of embodiments disclosed herein include gastrointestinalbleeding studies, gall bladder ejection fraction studies, and dynamicbone studies.

It may be noted that, while in some embodiments detectors may rotatewith a gantry and/or with respect to each other, in other embodimentsdetectors may not rotate about a patient. For example, in someembodiments, an imaging system is provided that includes a plurality ofdetector units, each fitted with a pinhole detector. The camera of suchan imaging system may be configured to acquire a 3D image of a FOVsmaller than an entire Region Of Interest (ROI). Additionally oralternatively, the ROI may be composed of several sub-ROIs that are notcontiguous, such as two or more distinct organs (e.g., 2 kidneys, or 1or 2 kidneys and a bladder). While each sub-ROI may be smaller than theFOV, the totality of the ROI still may not fit within the FOV of thecamera due to positioning or separation of the sub-ROIs.

In various embodiments, to acquire a dynamic (4D) image of the ROI witha camera having a FOV smaller than the ROI, the FOV of the camera may berepeatedly moved in respect to the patient body (for example, by movingthe camera with respect to the patient, or, as another example, bymoving the patient with respect to the camera) such that two or moreportions of the ROI are scanned several times during the entireacquisition. It may be noted that motion of the FOV of the camera withrespect to the patient body may be in an axial direction, a transaxialdirection, a depth direction, or combination of two or more of axial,transaxial, or depth directions.

It may be noted that each sub-ROI may be imaged successively at timeintervals corresponding to the time during which an image is expected tonoticeably, significantly, or substantially change due to the dynamic ofa particular isotope with respect to an organ or organs of interest. Forexample, each sub-ROI may be successively imaged at time intervalsshorter than the expected time in which the image is expected tosubstantially change due to the dynamic of the radioisotope on the organ(or organs) in that sub-ROI. It may be noted that the time intervals mayvary according to the type of organ, a medical condition (e.g., type ofdisease), and/or other patient characteristics (e.g., age, weight, orgender, among others). Additionally, the time intervals may vary duringthe acquisition due to the nature of the dynamic evolution of theradioisotope within the patient. For example, the changes in thedistribution of the radioisotope in the body is often relatively rapidimmediately or shortly after the injection of the radioisotope into thebody, while the rate of changes in the distribution of the radioisotopein the body later is relatively slower. Thus, in some embodiments, thetime intervals between sub-ROIs may be relatively shorter at thebeginning of the acquisition and may be relatively longer at laterstages.

In some embodiments, each time interval in which a sub-ROI is visited islong enough to acquire data sufficient to form a medically meaningful,or diagnostically useful, image of the sub-ROI. In such cases, each“visit” of a sub-ROI may be reconstructed independently. However, insome embodiments, each visit to a sub-ROI may be too short to acquire alarge enough data set for a medically meaningful, or diagnosticallyuseful, image of the sub-ROI, and reconstruction of the sub-ROI may beperformed using information acquired during plural visits to thesub-ROI. Generally, the time required to acquire a medically meaningful(e.g., with low enough noise) SPECT image of a sub-ROI is longer thanthe time it takes acquire a medically meaningful planar image of thesame sub-ROI. Accordingly, in some embodiments, planar images of thesub-ROIs may be obtained. Alternatively, a synthetic planar image may becreated (using methods known in the art) from SPECT images. A dynamicimage created from these synthetic planar images may be more familiar toa radiologist or other practitioner reading the image. Additionally,synthetic planar images may have less noise than the correspondingslices of original SPECT images.

In various embodiments, a dynamic 3D (SPECT) distribution vs. time, or adynamic 2D (planar) distribution vs. time may be created from anacquired data set. To form a dynamic image, missing data of one or moresub-ROIs may be interpolated for the times in which each sub-ROI was notimaged (e.g., the times at which one or more other sub-ROIs wereimaged). In some embodiments, interpolation may be achieved by modelingthe dynamics of the image in a sub-ROI over the time of interest fromseveral imaging information datasets that were acquired at correspondingdifferent times. Further, in some embodiments, isotope half-life may becompensated for. Further still, other known or measured effects (e.g.,the behavior of the distribution in non-target (or background) tissue)may be compensated for.

In various embodiments, data utilized for background subtraction may beacquired later in the acquisition, or even after the dynamic acquisitionhas ended, and the distribution of radioisotope is stable or slowlychanging. Such measurements may include imaging of non-target tissue orout-of-ROI tissue, and may be used for removing image artifacts as knownin the art.

A technical effect provided by various embodiments includes improvedimaging, for example improved NM imaging for dynamic studies. Atechnical effect of various embodiments includes allowing performance ofdynamic imaging of one or more ROI's that are larger than an axial fieldof view of a camera. A technical effect of various embodiments includesproviding simultaneous, concurrent, or temporally interleavedacquisition of NM imaging information for two or more FOV's.

FIG. 1 provides a schematic view of an imaging system 100 formed inaccordance with various embodiments. The depicted imaging system 100includes a gantry 110, nuclear medicine (NM) imaging detectors 120disposed about the gantry 110, a bed 130, a processing unit 140, acomputed tomography (CT) acquisition unit 150, an input unit 160, and adisplay unit 170. The processing unit 140 in the illustrated embodimentis configured to control the various components to acquire imaginginformation and to reconstruct one or more images. For example, theprocessing unit 140 may control the bed 130 and gantry 110 to acquireimaging information for a dynamic study of a ROI having an axial FOVlarger than the axial FOV of the detectors 120.

In the illustrated embodiment, a patient 102 is disposed on the bed 130for performance of a dynamic renal study. The patient 102 has a firstkidney 103, a second kidney 104, and a bladder 105. As seen in FIG. 1,the first kidney 103 and second kidney 104 are located at differentheights relative to the pelvis of the patient 102, for example due toone of the kidneys being transplanted. Further, as seen in FIG. 1, thedetectors 120 of the gantry 110 define an axial FOV having a width 122.As shown in FIG. 1, the width 122 of the axial FOV of the detectors 120is not sufficient to cover the first kidney 103, second kidney 104, andbladder 105 at the same time. For example, the width 122 may be about 20centimeters. Accordingly, to dynamically image the first kidney 103,second kidney 104, and bladder 105, the bed 130 may first be actuatedalong the axis of the bore 112 in a first direction 132 until the firstkidney 103 is within the FOV of the detectors 120 at a first axialposition 133 (in the first axial position 133, the gantry 110 anddetectors 120 are positioned about the first kidney 103). The bed 130may then be actuated further in the first direction 132 until the secondkidney 104 and the bladder 105 are within the FOV of the detectors 120at a second axial position 135 to collect imaging information for thesecond kidney 104 and bladder 105 (at the second axial position 135, thegantry 110 and detectors 120 are positioned about the second kidney 104and bladder 105). Then the bed 130 may be moved back and forth alongfirst direction 132 and second direction 131 (either generallycontinuously or in a series of steps) to acquire imaging information ofthe two FOV's in a temporally interleaved fashion, with the detectors120 rotated about the gantry 110 during different points of the cyclingback and forth to provide a variety of views for each detector 120. Itmay be noted that, in some embodiments, the detectors may be configuredas a multiple-pinhole based camera or other configuration that need notnecessarily rotate during an imaging process (e.g., the gantry or othersupport structure may not rotate during imaging, with only the bedarticulated along an axial direction during acquisition of imaginginformation).

The depicted input unit 160 is configured to obtain input correspondingto a scan to be performed, with the processing unit 140 using the inputto determine one or more scan settings (e.g., distance(s) for axialtranslation between steps, angular ranges for rotational steps, lengthor duration of imaging steps, length or duration of entire imagingprocess, or the like). The input unit 160 may include a keyboard, mouse,touchscreen or the like to receive input from an operator, and/or mayinclude a port or other connectivity device to receive input from acomputer or other source. The display unit 170 is configured to provideinformation to the user. The display unit 170 may be configured todisplay, for example, one or more images reconstructed by the processingunit 140 (e.g., images for dynamic studies). The images may be displayedat or near a time of acquisition and/or may be displayed or stored fordisplay at a later time. The display unit 170 may include one or more ofa screen, a touchscreen, a printer, or the like.

The depicted gantry 110 is configured as a rotating gantry. The gantry110 rotates about the bore 112. The detectors 120 are attached to thegantry 110, and rotate with the gantry 110, so that rotation of thegantry 110 provides different rotational positions for the detectors 120to provide different views from the detectors 120. Imaging informationof an object or portion thereof disposed within the bore of the gantry110 may be collected, detected, or acquired by the detectors 120.

The detectors 120 are positioned about the gantry 110 and are configuredto rotate with the gantry 110. For example, as seen in FIG. 2, thedetectors 120 are disposed about the bore 112 of the gantry 110. Thedetectors 120 have an axial FOV (e.g., shown as having width 122 inFIG. 1) as well as an in-plane field of view 125 shown in FIG. 2. Thewidth of the in-plane field of view 125 may be understood as extendingacross a portion of a plane that is transverse to an axis passingthrough the bore 112 of the gantry 110. The in-plane field of view thusmay be understood as extending in a direction transverse and/orperpendicular to the direction in which the axial field of view extends.In the illustrated embodiment, the in-plane field of view 125 generallycorresponds to the width of the detector head. For example, thedetectors 120 may include parallel-hole collimators associatedtherewith. As seen in FIG. 1, with the detectors 120 disposed about theupper half of the bore 112 (e.g., above the bed 130 and patient 102)being used to acquire imaging information, a gap 126 is defined betweenadjacent detectors 120. Due to the gap 126 and the generally verticalorientation of the in-plane FOV 125 of each detector, the in-plane fieldof view 125 of each detector 120 does not overlap with the in-plane FOVof immediately adjacent detectors 120. To collect imaging informationover the gaps 126, the detectors 120 may be rotated about the bore andused to collect imaging information in a series of steps until allportions of the gaps 126 have been covered. (For additional detailsregarding rotation of detectors in steps, see discussion below regardingFIGS. 2-4.)

Each detector 120 may include a detection surface constructed fromdetector tiles. The detector tiles may be CZT wafer detectors havingpixels or anodes. The pixels may be sized and positioned the same asholes of an associated parallel-hole collimator and may be registeredwith the holes in some embodiments, or have different numbers orpositions than the holes in other embodiments.

Further, each detector 120 may be configured as a detector headassembly, for example, a rotating head detector assembly. Thus, thedetectors 120 may rotate or pivot with respect to each other and thegantry 110, in addition to rotating about the bore 112 with the gantry110. For example, the detectors 120 may be maintained in aligned (e.g.,all detectors substantially vertical as shown in FIG. 2) fashion witheach other to acquire planar imaging information, and rotated or pivotedwith respect to each other to acquire SPECT information. The rotatinghead detector assembly may be pivotally attached to a telescoping arm(not shown in FIG. 1 or 2). The detector head assembly may also includeone or more analog front ends (AFE), as well as a digital readout board(DRB).

Returning to FIG. 1, the bed 130 is configured to support the patient102 during imaging and also to move the patient 102 axially duringimaging to position a desired portion of the patient 102 within the bore112 of the gantry 110. The bed 130 may be translated using an actuationmechanism such as a motor coupled to a rack and pinion, or as anotherexample, a cylinder. For example, in the illustrated embodiment, the bed130 is configured to be translated between the first axial position 133(at which the first kidney 103 is within the axial FOV of the detectorsbut the second kidney 104 and bladder 105 are not) and the second axialposition 135 (at which the second kidney 104 and bladder 105 are withinthe axial FOV of the detectors but the first kidney 103 is not). The bed130 in various embodiments may also be positioned at intermediatepositions between the first and second axial positions during imaging.The bed 130 may be moved in a series of steps between the first andsecond axial positions, or may be moved continuously between the firstand second axial positions during imaging.

The depicted processing unit 140 is operably coupled to the gantry 110,the detectors 120, the bed 130, the CT acquisition unit 150, the inputunit 160, and the display unit 170. The processing unit 140, forexample, may receive information from the input unit 160 describing orcorresponding to a procedure or study to be performed on one or moreorgans of interest. The processing unit 140 may then determine whichorgans to locate for scanning, and control the CT acquisition unit 150to perform a scout scan on the patient 102. Based on the scout scan, theprocessing unit 140 may determine the location of the organ or organs tobe imaged, and select axial positions for the bed 130 relative to thegantry 110 for acquiring imaging information. The processing unit maythen control the gantry to rotate the detectors 120 and translate thebed 130 pursuant to an imaging strategy for covering a FOV larger thanan axial FOV of the detectors 120. Using information from the detectors120, the processing unit 140 may then reconstruct an image and displaythe image via the display unit 170. The processing unit 140 may includeprocessing circuitry configured to perform one or more tasks, functions,or steps discussed herein. It may be noted that “processing unit” asused herein is not intended to necessarily be limited to a singleprocessor or computer. For example, the processing unit 140 may includemultiple processors and/or computers, which may be integrated in acommon housing or unit, or which may distributed among various units orhousings.

As seen in FIG. 1, in the illustrated embodiment, the processing unit140 includes a determination module 142, a control module 144, areconstruction module 146, and a memory 148. Generally, thedetermination module 142 may determine the axial and rotationalpositions to be used in acquiring NM imaging information (e.g., based onprotocol or procedure information from the display unit 170, and/orinformation from a scout scan, among others), as well as the steps to beused between the various axial and rotational positions). The controlmodule 144, for example, may formulate and provide control signals toimplement the acquisition steps determined by the determination module142 (e.g., rotate the gantry 110, axially translate the bed 130, controlthe detectors 120 to acquire NM information). The reconstruction module146 receives acquired NM imaging information from the detectors 120 andprovides a viewable or otherwise usable image or images to apractitioner. It may be noted that the particular units or modules shownin FIG. 1 are meant by way of example, and that other arrangements ofunits or sub-units of the processing unit 140 may be employed in variousembodiments. Further, other types, numbers, or combinations of modulesmay be employed in alternate embodiments, and/or various aspects ofmodules described herein may be utilized in connection with differentmodules additionally or alternatively. Generally, the various aspects ofthe processing unit 140 act individually or cooperatively with otheraspects to perform one or more aspects of the methods, steps, orprocesses discussed herein.

In various embodiments, the depicted processing unit 140 is configuredto acquire first NM imaging information of an object to be imaged (e.g.,patient 102) with the detectors 120 at a first rotational position(e.g., rotational position 200 shown in FIG. 2) and a first axialposition (e.g., axial position 133 shown in FIG. 1). The processing unit140 of the illustrated embodiment is also configured to iterativelyactuate the gantry 110 in a series of steps between the first rotationalposition (e.g., rotational position 200 shown in FIG. 2) and a secondrotational position (e.g., one or more additional rotational positionsconfigured to provide imaging information for areas corresponding to thegaps 126 between in-plane FOV's 125 of the detectors 120), as well asbetween the first axial position (e.g., axial position 133) and a secondaxial position (e.g., axial position 135). It may be noted that, as usedherein, actuation of a component relative to the gantry may beunderstood as an actuation of the gantry. During the iterative actuationof the gantry 110, the processing unit 140 may acquire additional NMinformation (e.g., via detectors 120) of the object at each iterativestep. Further, the depicted processing unit 140 is configured toreconstruct an image of the object using the first NM imaginginformation and the additional NM imaging information. With thedetectors 120 positioned over two or more axial FOV's at different timesduring a single imaging information acquisition process (e.g., a processcorresponding to a time of interest for a dynamic study), thereconstructed image has or corresponds to an axial FOV that is largerthan the axial FOV (e.g., width 122) of the detectors 120. It may benoted that the “image” need not necessarily be limited to a singleprinted or otherwise displayed page or screen. The image for example,may be dynamically presented to a viewer (e.g., via display unit 170)during the acquisition process. The information used to reconstruct orpresent the image may be understood as being collected during a single,generally continuous acquisition or scanning process.

It may be noted that actuation of the gantry 110 as used herein need notnecessarily involve movement of the gantry 110, but may also includemovement of an object or component relative to the gantry 110. Forexample, to actuate the gantry 110 between the first and second axialpositions, the bed 130 may be axially translated relative to the gantry110. As used herein, iteratively actuating the gantry 110 between axialpositions and rotational positions requires actuating the gantry 110(e.g., via motion of the bed 130) back and forth between axial positionas well as among rotational positions (e.g., via rotation of the gantry)multiple times for a single imaging or scanning process (e.g., dynamicstudy).

Thus, for example, imaging information for a first axial FOV (e.g.,corresponding to kidneys) may be acquired at times t1, t3, t5, and t7,and imaging information for a second axial FOV (e.g., corresponding tothe bladder) may be acquired at times t2, t4, t6, and t8. Thus, over aduration of an imaging time extending from time t1 to time t8, imaginginformation is collected alternately for the first and second axialFOV's, such that the imaging information may be understood as beingacquired in a temporally interleaved fashion. Thus, the times ofacquisition for each FOV overlap with each other. By collecting imaginginformation in a temporally interleaved fashion, imaging information forboth axial FOV's may be acquired over the same time period or durationfor dynamic studies, instead of collecting all information for one FOVat a first time and all information for a second FOV at a second,discrete, non-overlapping time. For the purposes of clarity andavoidance of doubt, translating a detector along a single helical pathin a given orientation is not iteratively actuating the gantry 110 asused herein. As another example, for the purposes of clarity and theavoidance of doubt, merely collecting a group of imaging information ata first axial FOV, and subsequently collecting a group of imaginginformation at a second axial FOV, without collecting information forboth FOV's in a temporally interleaved fashion, is not iterativelyactuating the gantry 110 as used herein.

The processing unit 140 may also be configured to determine the sizeand/or number of steps (rotational and/or axial) to be employed as partof the iterative actuation. For example, one or more organs of interestmay be identified from information acquired using SPECT (e.g., using thedetectors 120) and/or using CT (e.g., via a scout scan performed usingthe CT acquisition unit 150). The processing unit 140 may then determinean overall area to be scanned, as well as the relative spacing of anyorgans to determine if overlapping, adjacent, or spaced apart FOV's areto be used. As another example, the size or angular displacement ofrotational steps may be selected so that, for each detector, asubsequent FOV (e.g., the in-plane FOV for the next step) overlaps orborders the FOV of the preceding position. With the size of therotational steps determined, the number of rotational steps may bedetermined so that the entire gap between each pair of adjacentdetectors is covered.

An example of rotational steps for planar imaging (e.g., with thedetectors maintained in an aligned fashion among the various rotationalsteps) will now be discussed with particular reference to FIGS. 2-4.Detectors 120 disposed about the bore 112 of a gantry are shown in afirst rotational position 200 in FIG. 2. Each active detector 120 has anin-plane field of view 125 as seen in FIG. 2, with in-plane field ofview 125 being generally vertically oriented and having a width 124. Forthe example discussed in connection with FIGS. 2-4, the detectors 120are maintained in a generally vertical orientation for collection ofplanar imaging. For SPECT imaging, the detectors 120 could be pivoted orswept (e.g., pivoted in one or more directions to angular orientationsat an angle to the vertical orientation shown in FIG. 2) while at eachof the rotational positions of the gantry. Gaps 126 are present betweenin-plane FOV's 125 of adjacent detectors 120. Generally, the larger thepatient or object to be imaged, the farther outward radially thedetectors 120 will be positioned, and the larger the gaps 126 will be.Thus, additional rotational steps may be required for a larger patientthan for a smaller patient.

FIG. 3 illustrates the detectors 120 at a second rotational position300. The detectors 120 have been rotated clockwise relative to the firstrotational position 200 shown in FIG. 2. For the detector 120 a, forexample, the in-plane FOV 127 at the second rotational position 300 isdisposed generally to the right of (but still overlapping at leastslightly) the in-plane FOV 125 corresponding to the first rotationalposition 200. Thus, additional imaging information may be acquiredcorresponding to the FOV 127 to supply information for some, but notall, of the gap 126. Because portions of the gap 126 are not covered byeither the FOV 125 or the FOV 127, a subsequent third step may beemployed for complete coverage.

FIG. 4 illustrates the detectors 120 at a third rotational position 400.The detectors 120 have been rotated clockwise relative to the secondrotational position 300 shown in FIG. 3. For the detector 120 a, forexample, the in-plane FOV 129 at the third rotational position 400 isdisposed generally to the right of (but still overlapping at leastslightly) the in-plane FOV 127 corresponding to the second rotationalposition 300. As seen in FIG. 4, for the illustrated embodiment, the FOV129 fills the remainder of the corresponding gap 126, so that additionalrotational steps may not be needed to complete the particularcorresponding gap. When all gaps for all detectors are covered by FOV'sfor the various steps (or at least all gaps disposed above a patient orwith the patient within a field of view), additional rotational stepsare not required. The first rotational step 200, second rotational step300, and third rotational step 400 may be understood as providingrotation over a full imaging range, as the first rotational step 200,second rotational step 300, and third rotational step 400 providesufficient rotation to cover the gaps between the detectors (e.g., thegaps between the in-plane FOV's in the first rotational position). Thefirst rotational position 200 and third rotational positon 400 provideexamples of end rotational positions, and the second rotational position300 provides an example of an intermediate rotational position.

The particular order in which rotational and/or axial steps are takenand/or interleaved may vary in different embodiments. For example, inone example, the gantry 110 may be rotated over the steps of a fullimaging range while at a first axial position (e.g., axial position 133in FIG. 1). Then, the gantry and detectors may be advanced to a secondaxial position (e.g., axial position 135 in FIG. 1), for example bymoving the bed 130 axially relative to the gantry 110. At the secondaxial position, the gantry may then be rotated over the steps of a fullimaging range in a reverse direction to that performed at the firstaxial position. For example, if the gantry is rotated clockwise at thefirst axial position, the gantry may be rotated counterclockwise at thesecond axial position, for example to avoid having to return thedetectors to the first rotational position before starting imaging atthe second axial position. An example of the locations of the detectorsfor each imaging step in the first series of an iterative process, withreference to the axial positions described in connection with FIG. 1 andthe rotational positions described in connection with FIGS. 2-4, isshown below. Additional steps may be provided or iteratively repeated asdesired to provide a desired amount or duration of time of imaginginformation.

Step Rotational Position Axial Position 1 200 133 2 300 133 3 400 133 4400 135 5 300 135 6 200 135 7 200 133 8 300 133 . . .

In some embodiments, the gantry may be rotated over less than a fullimaging range before adjusting axial position. An example of thelocations of the detectors for each imaging step in the first series inan iterative process for which less than a full imaging range is coveredbefore adjusting axial position is shown in the table below, withcontinued reference to the axial positions described in connection withFIG. 1 and the rotational positions described in connection with FIGS.2-4 is shown below. Again, additional steps may be performed as desiredto provide a desired amount or duration of time of imaging information.

Step Rotational Position Axial Position 1 200 133 2 200 135 3 300 135 4300 133 5 400 133 6 400 135 7 200 135 8 200 133 . . .

It should be noted that the above examples are provided for illustrativepurposes, and that other arrangements of steps may be employed invarious embodiments. For example, in some embodiments, additional and/orsmaller steps may be employed. For instance, in some embodiments,intermediate axial positions may be provided between first and secondaxial positions.

Further still, it may be noted that the motion in the rotational and/oraxial directions may be generally continuous in various embodiments.FIG. 5 illustrates a curve 500 that plots bed position (e.g., along anaxis of the bore of a gantry) against time. In the example of FIG. 5,the bed is advanced in a generally continuous fashion during acquisition(e.g., in continuous motion between endpoints). The curve 500 isgenerally sinusoidal in the illustrated embodiment, but other motionsmay be employed in alternate embodiments. As seen in FIG. 5, the slopeof the curve 500 is substantially smaller proximate transition points502, 504 corresponding to changes in direction. Thus, the movement ofthe bed may be slower at ends where the bed switches from one directionto the other to provide less or no jarring to a patient during changesin direction, while providing faster movement over the middle portion506 of the range of motion to reduce time of travel when not asdiscomforting to patient. The particular speeds of the bed andconfiguration of the curve 500 may be tailored to a given application toprovide desired levels of patient comfort as well as to reduce orminimize blurring of images acquired during motion of the bed (e.g., byreducing speed at end points of travel and/or during acquisition). Thus,in some embodiments, the gantry may be actuated in a step and shootfashion with the bed and gantry stationary during image acquisition,while in other embodiments, actuation in at least one direction (e.g.,axial) may be generally continuous during acquisition.

As discussed above in connection with FIG. 2-4, planar imagingacquisition may be performed in accordance with various embodiments.Additionally or alternatively, three-dimensional (e.g., SPECT)acquisition may be performed in some embodiments. For example, thedetectors 120 may be pivoted or rotated relative to each other to sweepover a range. The additional view angles for the detectors may be usedto provide three-dimensional imaging capabilities.

In some embodiments, the processing unit 140 may be configured tocontrol the detectors to sweep over a first smaller range to collectadditional information for the first smaller range relative to a secondlarger range, thereby acquiring sufficient information for providing ahigher quality image for a region of interest positioned in the firstsmaller range, while reducing the overall time required for an imagingscan and/or making the most efficient use of a limited acquisition timefor imaging an organ of interest.

For example, FIG. 6 depicts varying coverage of sweep ranges of adetector over the duration of an imaging scan. In FIG. 6 an object 600includes an organ of interest 602 (e.g., a heart) and a supplementalvolume 604 (e.g., portions of the object other than the heart that mayprovide useful background or comparison information). The pivot angle ofa detector (e.g., detector 120) is selectively controlled to pivot overa first pivoting range 610 that provides coverage of the organ ofinterest 602, and over a second pivoting range 620 that providescoverage of the organ of interest 602 as well as the supplemental volume604. As seen in FIG. 6, a larger proportion of the acquisition time isspent pivoting the detector over the first pivoting range 610 than overthe second pivoting range 620. Further, the time spent on the firstpivoting range 610 may be biased toward the beginning 625 of theacquisition duration 630, so that more information regarding the organof interest 602 may be acquired during a time period of greaterinformational value or relatively quickly varying time period for whichimaging information of the organ of interest 602 is particularly desired(e.g., during an uptake or washout phase), with imaging information forthe supplemental volume 604 acquired at a less valuable or more slowlyvarying time period.

FIG. 7 illustrates a first imaging system 700 and a second imagingsystem 750 that includes detectors 710 mounted on arms 720 about a bore730. The first imaging system 700 includes arms 720 distributedgenerally uniformly about the bore 730, while the second imaging system750 includes arms 720 disposed only about a portion of the bore 730. InFIG. 7, the detectors 710 are disposed on arms 720 that extend radiallyacross the bore 730. It may be noted that other arrangements of arms anddetectors may be employed. For example, the arms may be arranged in agenerally horizontal and/or vertical direction relative to the bore 730(see, e.g., FIG. 10).

In some embodiments, NM imaging information may be acquired at twodistinct axial FOV's simultaneously, alternatively or in addition to ina temporally interleaved fashion as discussed above. FIG. 8 illustratesan imaging system 800 configured to acquire simultaneous NM imaginginformation for two axial FOV's. The imaging system 800 includes a bed810 on which a patient 802 to be imaged is supported. The bed 810 iscoupled to an actuating mechanism 820 that articulates the bedvertically along direction 822 and horizontally (or axially into and outof the bore) along direction 824. The imaging system also includes afixed gantry 830 and a movable gantry 840. The fixed gantry 830 andmovable gantry 840 share an aligned bore 832. Each gantry includesdetectors (e.g., detectors 120) not shown in FIG. 8 that may rotate withthe gantry and be used to collect NM imaging information. The fixedgantry 830 may be referred to as fixed because the fixed gantry 830 ismounted to a floor or other support structure and is not axiallyadjustable (e.g., along direction 824), while the movable gantry 840 isadjustable axially. Thus, the bed 810 and movable gantry 840 may beaxially adjusted relative to the fixed gantry 830, and relative to eachother. It may be noted that, in some embodiments, the detectors of oneor more of the gantries may be configured as a multiple-pinhole basedcamera or other configuration that need not necessarily rotate with agantry or other support structure (e.g., the gantry or other supportstructure may not rotate during imaging, with only the bed articulatedalong an axial direction during acquisition of imaging information).

To image multiple axial FOV's simultaneously, the bed 810 may beadvanced into the bore 832 until a first ROI is disposed within thefixed gantry 830. Then, the movable gantry 840 may be adjusted until asecond ROI of the patient 802 is disposed within the movable gantry 840.Thus, information for two ROI's or FOV's spaced apart from each axiallymay be simultaneously acquired by operating the detectors of the fixedgantry 830 and the detectors of the movable gantry 840 to acquire NMimaging information with the gantries positioned about the differentROI's.

FIG. 9 provides a flowchart of a method 900 for imaging (e.g.,dynamically imaging). The method 900, for example, may employ or beperformed by structures or aspects of various embodiments (e.g., systemsand/or methods) discussed herein. In various embodiments, certain stepsmay be omitted or added, certain steps may be combined, certain stepsmay be performed simultaneously, certain steps may be performedconcurrently, certain steps may be split into multiple steps, certainsteps may be performed in a different order, or certain steps or seriesof steps may be re-performed in an iterative fashion. In variousembodiments, portions, aspects, and/or variations of the method 900 maybe able to be used as one or more algorithms to direct hardware toperform one or more operations described herein.

At 902, a scanning protocol is determined. For example, the scanningprotocol may be determined based on information provided by a user viaan input unit (e.g., input unit 160).

At 904, the location of one or more target organs is determined. Forexample, for a dynamic renal study, the kidneys and bladder may beidentified as the target organs. The target organs may be identifieddirectly by a user input, and/or determined based on user input. Thelocation of the target organs may be determined using imaginginformation, such as SPECT imaging information and/or CT imaginginformation. For example, in some embodiments, a scout image may be usedto determine organ location. In the illustrated embodiment, at 906,organ location information is obtained from a CT acquisition unit, forexample by performing a scout scan. The location of the organs ofinterest may be determined using computer software configured toidentify organs from scout images, or may be identified by a user (e.g.,via an input to a touch screen displaying a scout image).

At 908, settings for the performance of imaging acquisition are set. Thesettings may be based, for example, on the protocol selected ordetermined at 902 as well as the location of the one or more targetorgans determined at 904. The settings may specify, for example, variousrotational and axial positions to be employed during the scan, as wellas the time to be spent at each position, the order in which thepositions are to be used to acquire imaging information or the like.Generally, an imaging system may be controlled pursuant to the settingsto collect information for plural FOV's in a temporally interleavedfashion so that information for each FOV is collected during at least aportion of a shared time duration. For example, if a period of interesthas a duration of about 20 seconds, information from each FOV may becollected during a portion of the about 20 seconds, providing forimproved consistency between the images for each FOV and improveddiagnostic value in comparisons between the FOV's relative to studieswhere images for different FOV's are acquired at separate,non-overlapping times.

At 910, first NM imaging information is acquired of an object to beimaged at a first end rotational position and a first axial position ofan imaging system (e.g., imaging system 100). The first NM imaginginformation may be acquired, for example, shortly after introduction ofa radiopharmaceutical for NM imaging is introduced into a patient to beimaged. It may be noted that an “end rotational” position may beunderstood as being an end position in that it corresponds to abeginning or an end of a cycle of movement between positions, and neednot necessarily be physically disposed at an end of a range of motion.For example, in some embodiments, a first end rotational position, atwhich first NM imaging information is obtained, may be disposed at amiddle or other intermediate physical position with respect to a rangeof rotation.

At 912, a gantry of the imaging system is actuated iteratively in aseries of steps between the first end rotational position and a secondend rotational position as well as between the first axial position anda second axial position. Additional NM imaging information may beacquired at each step. The axial positions may correspond to differentFOV's along an axis of the object (the FOV's may be adjacent,overlapping, or spaced apart), and the rotational positions may beconfigured to provide a full imaging range (e.g., to account for anygaps between in-plane FOV's of detectors). As discussed herein, forexample, at least some of the actuations (e.g., motion of a bed axially)may be performed in a generally continuous fashion (e.g., to reducepatient discomfort caused by repeated starting and stopping of a bed (at918). Further in some embodiments, a full imaging range of rotationalsteps may be acquired before adjusting an axial position (at 914), whilein other embodiments less than a full imaging range of rotational stepsmay be acquired between axial adjustments (at 916). In some embodiments,detectors may be maintained aligned or parallel to obtain planar NMimaging information. Additionally or alternatively, in some embodiments,detectors may be pivoted with respect to each other or swept for some orall acquisition steps to provide three-dimensional imaging information(at 920). For example, detectors may be swept over a first pivotingrange corresponding to an organ of interest for more time than over asecond pivoting range corresponding to a supplement volume during animaging or scanning process.

At 922, an image is reconstructed using the information acquired at 910and 912. It may be noted that the “image” need not necessarily belimited to a single printed or otherwise displayed page or screen. Theimage for example, may be dynamically presented to a viewer (e.g., viadisplay unit 170) during the acquisition process. The information from910 and 912 used to reconstruct or present the image may be understoodas being collected during a single, generally continuous acquisition orscanning process. For example, the information acquired for two or moreaxial FOV's may be acquired in a temporally interleaved fashion asdiscussed herein, in contrast to separate imaging process performed atdistinct and non-overlapping time frames for two or more FOV's.

Various methods and/or systems (and/or aspects thereof) described hereinmay be implemented using a medical imaging system. For example, FIG. 10is a schematic illustration of a NM imaging system 1000 having aplurality of imaging detector head assemblies mounted on a gantry (whichmay be mounted, for example, in rows, in an iris shape, or otherconfigurations, such as a configuration in which the movable detectorcarriers 1016 are aligned radially toward the patient-body 1010). Inparticular, a plurality of imaging detectors 1002 are mounted to agantry 1004. Each detector 1002 may include, for example, collimatorsand detectors arranged generally similarly to the arrangements discussedin connection with FIGS. 1-9. In the illustrated embodiment, the imagingdetectors 1002 are configured as two separate detector arrays 1006 and1008 coupled to the gantry 1004 above and below a subject 1010 (e.g., apatient), as viewed in FIG. 10. The detector arrays 1006 and 1008 may becoupled directly to the gantry 1004, or may be coupled via supportmembers 1012 to the gantry 1004 to allow movement of the entire arrays1006 and/or 1008 relative to the gantry 1004 (e.g., transversetranslating movement in the left or right direction as viewed by arrow Tin FIG. 10). Additionally, each of the imaging detectors 1002 includes adetector unit 1014, at least some of which are mounted to a movabledetector carrier 1016 (e.g., a support arm or actuator that may bedriven by a motor to cause movement thereof) that extends from thegantry 1004. In some embodiments, the detector carriers 1016 allowmovement of the detector units 1014 towards and away from the subject1010, such as linearly. Thus, in the illustrated embodiment the detectorarrays 1006 and 1008 are mounted in parallel above and below the subject1010 and allow linear movement of the detector units 1014 in onedirection (indicated by the arrow L), illustrated as perpendicular tothe support member 1012 (that are coupled generally horizontally on thegantry 1004). However, other configurations and orientations arepossible as described herein. It should be noted that the movabledetector carrier 1016 may be any type of support that allows movement ofthe detector units 1014 relative to the support member 1012 and/organtry 1004, which in various embodiments allows the detector units 1014to move linearly towards and away from the support member 1012.

Each of the imaging detectors 1002 in various embodiments is smallerthan a conventional whole body or general purpose imaging detector. Aconventional imaging detector may be large enough to image most or allof a width of a patient's body at one time and may have a diameter or alarger dimension of approximately 50 cm or more. In contrast, each ofthe imaging detectors 1002 may include one or more detector units 1014coupled to a respective detector carrier 1016 and having dimensions of,for example, 4 cm to 20 cm and may be formed of Cadmium Zinc Telluride(CZT) tiles or modules. For example, each of the detector units 1014 maybe 8×8 cm in size and be composed of a plurality of CZT pixelatedmodules (not shown). For example, each module may be 4×4 cm in size andhave 16×16=256 pixels. In some embodiments, each detector unit 1014includes a plurality of modules, such as an array of 1×7 modules.However, different configurations and array sizes are contemplatedincluding, for example, detector units 1014 having multiple rows ofmodules.

It should be understood that the imaging detectors 1002 may be differentsizes and/or shapes with respect to each other, such as square,rectangular, circular or other shape. An actual field of view (FOV) ofeach of the imaging detectors 1002 may be directly proportional to thesize and shape of the respective imaging detector.

The gantry 1004 may be formed with an aperture 1018 (e.g., opening orbore) therethrough as illustrated. A patient table 1020, such as apatient bed, is configured with a support mechanism (not shown) tosupport and carry the subject 1010 in one or more of a plurality ofviewing positions within the aperture 1018 and relative to the imagingdetectors 1002. Alternatively, the gantry 1004 may comprise a pluralityof gantry segments (not shown), each of which may independently move asupport member 1012 or one or more of the imaging detectors 1002.

The gantry 1004 may also be configured in other shapes, such as a “C”,“H” and “L”, for example, and may be rotatable about the subject 1010.For example, the gantry 1004 may be formed as a closed ring or circle,or as an open arc or arch which allows the subject 1010 to be easilyaccessed while imaging and facilitates loading and unloading of thesubject 1010, as well as reducing claustrophobia in some subjects 1010.

Additional imaging detectors (not shown) may be positioned to form rowsof detector arrays or an arc or ring around the subject 1010. Bypositioning multiple imaging detectors 1002 at multiple positions withrespect to the subject 1010, such as along an imaging axis (e.g., headto toe direction of the subject 1010) image data specific for a largerFOV may be acquired more quickly.

Each of the imaging detectors 1002 has a radiation detection face, whichis directed towards the subject 1010 or a region of interest within thesubject.

The collimators 1022 (and detectors) in FIG. 10 are depicted for ease ofillustration as single collimators in each detector head. Optionally,for embodiments employing one or more parallel-hole collimators,multi-bore collimators may be constructed to be registered with pixelsof the detector units 1014, which in one embodiment are CZT detectors.However, other materials may be used. Registered collimation may improvespatial resolution by forcing photons going through one bore to becollected primarily by one pixel. Additionally, registered collimationmay improve sensitivity and energy response of pixelated detectors asdetector area near the edges of a pixel or in-between two adjacentpixels may have reduced sensitivity or decreased energy resolution orother performance degradation. Having collimator septa directly abovethe edges of pixels reduces the chance of a photon impinging at thesedegraded-performance locations, without decreasing the overallprobability of a photon passing through the collimator.

A controller unit 1030 may control the movement and positioning of thepatient table 1020, imaging detectors 1002 (which may be configured asone or more arms), gantry 1004 and/or the collimators 1022 (that movewith the imaging detectors 1002 in various embodiments, being coupledthereto). A range of motion before or during an acquisition, or betweendifferent image acquisitions, is set to maintain the actual FOV of eachof the imaging detectors 1002 directed, for example, towards or “aimedat” a particular area or region of the subject 1010 or along the entiresubject 1010. The motion may be a combined or complex motion in multipledirections simultaneously, concurrently, or sequentially as described inmore detail herein.

The controller unit 1030 may have a gantry motor controller 1032, tablecontroller 1034, detector controller 1036, pivot controller 1038, andcollimator controller 1040. The controllers 1030, 1032, 1034, 1036,1038, 1040 may be automatically commanded by a processing unit 1050,manually controlled by an operator, or a combination thereof. The gantrymotor controller 1032 may move the imaging detectors 1002 with respectto the subject 1010, for example, individually, in segments or subsets,or simultaneously in a fixed relationship to one another. For example,in some embodiments, the gantry controller 1032 may cause the imagingdetectors 1002 and/or support members 1012 to move relative to or rotateabout the subject 1010, which may include motion of less than or up to180 degrees (or more).

The table controller 1034 may move the patient table 1020 to positionthe subject 1010 relative to the imaging detectors 1002. The patienttable 1020 may be moved in up-down directions, in-out directions, andright-left directions, for example. The detector controller 1036 maycontrol movement of each of the imaging detectors 1002 to move togetheras a group or individually as described in more detail herein. Thedetector controller 1036 also may control movement of the imagingdetectors 1002 in some embodiments to move closer to and farther from asurface of the subject 1010, such as by controlling translating movementof the detector carriers 1016 linearly towards or away from the subject1010 (e.g., sliding or telescoping movement). Optionally, the detectorcontroller 1036 may control movement of the detector carriers 1016 toallow movement of the detector array 1006 or 1008. For example, thedetector controller 1036 may control lateral movement of the detectorcarriers 1016 illustrated by the T arrow (and shown as left and right asviewed in FIG. 10). In various embodiments, the detector controller 1036may control the detector carriers 1016 or the support members 1012 tomove in different lateral directions. Detector controller 1036 maycontrol the swiveling motion of detectors 1002 together with theircollimators 1022, as shown for example in FIG. 3, or as shown bydetector 410 in FIG. 4, as another example. In some embodiments,detectors 1002 and collimators 1022 may swivel or rotate around an axis.

The pivot controller 1038 may control pivoting or rotating movement ofthe detector units 1014 at ends of the detector carriers 1016 and/orpivoting or rotating movement of the detector carrier 1016. For example,one or more of the detector units 1014 or detector carriers 1016 may berotated about at least one axis to view the subject 1010 from aplurality of angular orientations to acquire, for example, 3D image datain a 3D SPECT or 3D imaging mode of operation. The collimator controller1040 may adjust a position of an adjustable collimator, such as acollimator with adjustable strips (or vanes) or adjustable pinhole(s).

It should be noted that motion of one or more imaging detectors 1002 maybe in directions other than strictly axially or radially, and motions inseveral motion directions may be used in various embodiment. Therefore,the term “motion controller” may be used to indicate a collective namefor all motion controllers. It should be noted that the variouscontrollers may be combined, for example, the detector controller 1036and pivot controller 1038 may be combined to provide the differentmovements described herein.

Prior to acquiring an image of the subject 1010 or a portion of thesubject 1010, the imaging detectors 1002, gantry 1004, patient table1020 and/or collimators 1022 may be adjusted, such as to first orinitial imaging positions, as well as subsequent imaging positions. Theimaging detectors 1002 may each be positioned to image a portion of thesubject 1010. Alternatively, for example in a case of a small sizesubject 1010, one or more of the imaging detectors 1002 may not be usedto acquire data, such as the imaging detectors 1002 at ends of thedetector arrays 1006 and 1008, which as illustrated in FIG. 10 are in aretracted position away from the subject 1010. Positioning may beaccomplished manually by the operator and/or automatically, which mayinclude using, for example, image information such as other imagesacquired before the current acquisition, such as by another imagingmodality such as X-ray Computed Tomography (CT), MRI, X-Ray, PET orultrasound. In some embodiments, the additional information forpositioning, such as the other images, may be acquired by the samesystem, such as in a hybrid system (e.g., a SPECT/CT system).Additionally, the detector units 1014 may be configured to acquirenon-NM data, such as x-ray CT data. In some embodiments, amulti-modality imaging system may be provided, for example, to allowperforming NM or SPECT imaging, as well as x-ray CT imaging, which mayinclude a dual-modality or gantry design as described in more detailherein.

After the imaging detectors 1002, gantry 1004, patient table 1020,and/or collimators 1022 are positioned, one or more images, such asthree-dimensional (3D) SPECT images are acquired using one or more ofthe imaging detectors 1002, which may include using a combined motionthat reduces or minimizes spacing between detector units 1014. The imagedata acquired by each imaging detector 1002 may be combined andreconstructed into a composite image or 3D images in variousembodiments.

In one embodiment, at least one of detector arrays 1006 and/or 1008,gantry 1004, patient table 1020, and/or collimators 1022 are moved afterbeing initially positioned, which includes individual movement of one ormore of the detector units 1014 (e.g., combined lateral and pivotingmovement) together with the swiveling motion of detectors 1002. Forexample, at least one of detector arrays 1006 and/or 1008 may be movedlaterally while pivoted. Thus, in various embodiments, a plurality ofsmall sized detectors, such as the detector units 1014 may be used for3D imaging, such as when moving or sweeping the detector units 1014 incombination with other movements.

In various embodiments, a data acquisition system (DAS) 1060 receiveselectrical signal data produced by the imaging detectors 1002 andconverts this data into digital signals for subsequent processing.However, in various embodiments, digital signals are generated by theimaging detectors 1002. An image reconstruction device 1062 (which maybe a processing device or computer) and a data storage device 1064 maybe provided in addition to the processing unit 1050. It should be notedthat one or more functions related to one or more of data acquisition,motion control, data processing and image reconstruction may beaccomplished through hardware, software and/or by shared processingresources, which may be located within or near the imaging system 1000,or may be located remotely. Additionally, a user input device 1066 maybe provided to receive user inputs (e.g., control commands), as well asa display 1068 for displaying images. DAS 1060 receives the acquiredimages from detectors 1002 together with the corresponding lateral,vertical, rotational and swiveling coordinates of gantry 1004, supportmembers 1012, detector units 1014, detector carriers 1016, and detectors1002 for accurate reconstruction of an image including 3D images andtheir slices.

As used herein, a structure, limitation, or element that is “configuredto” perform a task or operation is particularly structurally formed,constructed, or adapted in a manner corresponding to the task oroperation. For purposes of clarity and the avoidance of doubt, an objectthat is merely capable of being modified to perform the task oroperation is not “configured to” perform the task or operation as usedherein. Instead, the use of “configured to” as used herein denotesstructural adaptations or characteristics, and denotes structuralrequirements of any structure, limitation, or element that is describedas being “configured to” perform the task or operation. For example, aprocessing unit, processor, or computer that is “configured to” performa task or operation may be understood as being particularly structuredto perform the task or operation (e.g., having one or more programs orinstructions stored thereon or used in conjunction therewith tailored orintended to perform the task or operation, and/or having an arrangementof processing circuitry tailored or intended to perform the task oroperation). For the purposes of clarity and the avoidance of doubt, ageneral purpose computer (which may become “configured to” perform thetask or operation if appropriately programmed) is not “configured to”perform a task or operation unless or until specifically programmed orstructurally modified to perform the task or operation.

It should be noted that the various embodiments may be implemented inhardware, software or a combination thereof. The various embodimentsand/or components, for example, the modules, or components andcontrollers therein, also may be implemented as part of one or morecomputers or processors. The computer or processor may include acomputing device, an input device, a display unit and an interface, forexample, for accessing the Internet. The computer or processor mayinclude a microprocessor. The microprocessor may be connected to acommunication bus. The computer or processor may also include a memory.The memory may include Random Access Memory (RAM) and Read Only Memory(ROM). The computer or processor further may include a storage device,which may be a hard disk drive or a removable storage drive such as asolid-state drive, optical disk drive, and the like. The storage devicemay also be other similar means for loading computer programs or otherinstructions into the computer or processor.

As used herein, the term “computer” or “module” may include anyprocessor-based or microprocessor-based system including systems usingmicrocontrollers, reduced instruction set computers (RISC), ASICs, logiccircuits, and any other circuit or processor capable of executing thefunctions described herein. The above examples are exemplary only, andare thus not intended to limit in any way the definition and/or meaningof the term “computer”.

The computer or processor executes a set of instructions that are storedin one or more storage elements, in order to process input data. Thestorage elements may also store data or other information as desired orneeded. The storage element may be in the form of an information sourceor a physical memory element within a processing machine.

The set of instructions may include various commands that instruct thecomputer or processor as a processing machine to perform specificoperations such as the methods and processes of the various embodiments.The set of instructions may be in the form of a software program. Thesoftware may be in various forms such as system software or applicationsoftware and which may be embodied as a tangible and non-transitorycomputer readable medium. Further, the software may be in the form of acollection of separate programs or modules, a program module within alarger program or a portion of a program module. The software also mayinclude modular programming in the form of object-oriented programming.The processing of input data by the processing machine may be inresponse to operator commands, or in response to results of previousprocessing, or in response to a request made by another processingmachine.

As used herein, the terms “software” and “firmware” are interchangeable,and include any computer program stored in memory for execution by acomputer, including RAM memory, ROM memory, EPROM memory, EEPROM memory,and non-volatile RAM (NVRAM) memory. The above memory types areexemplary only, and are thus not limiting as to the types of memoryusable for storage of a computer program.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the variousembodiments without departing from their scope. While the dimensions andtypes of materials described herein are intended to define theparameters of the various embodiments, they are by no means limiting andare merely exemplary. Many other embodiments will be apparent to thoseof skill in the art upon reviewing the above description. The scope ofthe various embodiments should, therefore, be determined with referenceto the appended claims, along with the full scope of equivalents towhich such claims are entitled. In the appended claims, the terms“including” and “in which” are used as the plain-English equivalents ofthe respective terms “comprising” and “wherein.” Moreover, in thefollowing claims, the terms “first,” “second,” and “third,” etc. areused merely as labels, and are not intended to impose numericalrequirements on their objects. Further, the limitations of the followingclaims are not written in means-plus-function format and are notintended to be interpreted based on 35 U.S.C. §112(f) unless and untilsuch claim limitations expressly use the phrase “means for” followed bya statement of function void of further structure.

This written description uses examples to disclose the variousembodiments, including the best mode, and also to enable any personskilled in the art to practice the various embodiments, including makingand using any devices or systems and performing any incorporatedmethods. The patentable scope of the various embodiments is defined bythe claims, and may include other examples that occur to those skilledin the art. Such other examples are intended to be within the scope ofthe claims if the examples have structural elements that do not differfrom the literal language of the claims, or the examples includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

What is claimed is:
 1. An imaging system comprising: a gantry having abore therethrough; a bed that is translatable between a first axialposition and a second axial position along an axis of the bore of therotating gantry, the bed configured to support an object to be imaged,the first axial position having a first field of view corresponding to afirst portion of the object, the second axial position having a secondfield of view corresponding to a second portion of the object that isdifferent from the first portion; plural nuclear medicine (NM) imagingdetectors disposed about the bore of the gantry, the NM imagingdetectors having an axial field of view; and a processing unit operablycoupled to the imaging detectors, the processing unit configured to:acquire first NM imaging information of the object from the imagingdetectors with the imaging detectors in the first axial position;iteratively actuate the gantry in a series of steps back and forthbetween the first axial position and the second axial position, whereinthe series of steps comprises plural steps at each of the first andsecond axial positions; acquire additional NM imaging information of theobject at each of the steps; and reconstruct an image of the objectusing the first NM imaging information and the additional NM imaginginformation, wherein the image corresponds to an axial field of viewthat is larger than the axial field of view of the imaging detectors. 2.The imaging system of claim 1, wherein the gantry is a rotating gantry,wherein the NM imaging detectors have an in-plane field of view, theimaging detectors having corresponding gaps therebetween wherein anin-plane field of view of each detector does not overlap withcorresponding in-plane fields of views of at least one immediatelyadjacent imaging detector, and wherein the processing unit is configuredto: acquire the first NM imaging information of the object from theimaging detectors with the imaging detectors in a first end rotationalposition and the first axial position; and iteratively actuate thegantry in a series of steps between the first end rotational positionand a second end rotational position, and between the first axialposition and the second axial position.
 3. The imaging system of claim2, wherein the processing unit is configured to rotate the gantry over afull imaging range in a first direction from the first end rotationalposition to the second end rotational position while the imagingdetectors remain at the first axial position, then advance the imagingdetectors to the second axial position, and then rotate the gantry overthe full imaging range in a second direction opposite to the firstdirection from the second end rotational position to the first endrotational position with the detectors at the second axial position,wherein rotating the gantry over the full imaging range corresponds to arotation of the gantry sufficient to provide imaging information overthe gaps between the in-plane fields of view of the imaging detectors.4. The imaging system of claim 2, wherein the processing unit isconfigured to rotate the gantry over less than a full imaging rangebefore adjusting an axial position, wherein rotating the gantry over thefull imaging range corresponds to a rotation of the gantry sufficient toprovide imaging information over the gaps between the in-plane fields ofview of the imaging detectors.
 5. The imaging system of claim 1, whereinthe processing unit is configured to axially oscillate the bed generallycontinuously over a duration of an imaging scan.
 6. The imaging systemof claim 5, wherein the processing unit is configured to oscillate thebed sinusoidally with respect to time during the duration of the imagingscan.
 7. The imaging system of claim 1, wherein the processing unit isconfigured to align the imaging detectors parallel with respect eachother during rotation, and wherein the image reconstructed is a planarimage.
 8. The imaging system of claim 1, wherein the processing unit isconfigured to rotate the imaging detectors relative to each other, andwherein the image reconstructed is a three-dimensional image.
 9. Theimaging system of claim 8, wherein a first pivoting range of thedetectors corresponds to an organ of interest and a second pivotingrange corresponds to a supplemental volume, wherein the processing unitis configured to sweep the detectors over the first pivoting range for alonger duration of time than over the second pivoting range duringperformance of an imaging scan.
 10. The imaging system of claim 1,further comprising a computed tomography (CT) detector, wherein theprocessing unit is configured to obtain organ location information fromthe CT detector, and to determine the first and second axial positionsbased on the organ location information.
 11. The method of claim 10further comprising obtaining organ location information from a computedtomography (CT) detector, and determining the first and second axialpositions based on the organ location information.
 12. A methodcomprising: acquiring first nuclear medicine (NM) imaging information ofan object to be imaged with plural NM imaging detectors at a first axialposition, the imaging detectors disposed about a gantry having a boretherethrough, with the object disposed on a bed translatable along anaxis of the bore between the first axial position and a second axialposition, the imaging detectors having an axial field of view, the firstaxial position defining a first field of view corresponding to a firstportion of the object, the second axial position defining a second fieldof view corresponding to a second portion of the object that isdifferent from the first portion; iteratively actuating the gantry in aseries of steps back and forth between the first axial position and thesecond axial position, wherein the series of steps comprises pluralsteps at each of the first and second axial positions; acquiringadditional NM imaging information of the object at each of the steps;and reconstructing an image of the object using the first NM imaginginformation and the additional NM imaging information, wherein the imagecorresponds to an axial field of view that is larger than the axialfield of view of the imaging detectors.
 13. The method of claim 12,wherein the first NM imaging information is acquired at the first axialposition and a first end rotational position, wherein the imagingdetectors have an in-plane field of view, the imaging detectors havingcorresponding gaps therebetween wherein an in-plane field of view ofeach detectors does not overlap with corresponding in-plane fields ofviews of at least one immediately adjacent imaging detector, and whereiniteratively actuating the gantry comprises iteratively actuating thegantry in a series of steps between the first end rotational positionand a second end rotational position, and between the first axialposition and the second axial position.
 14. The method of claim 13,wherein iteratively actuating the gantry comprises: rotating the gantryover a full imaging range in a first direction from the first endrotational position to the second end rotational position while theimaging detectors remain at the first axial position, wherein rotatingthe gantry over the full imaging range corresponds to a rotation of thegantry sufficient to provide imaging information over the gaps betweenthe in-plane fields of view of the imaging detectors; then advancing theimaging detectors to the second axial position; then rotating the gantryover the full imaging range in a second direction opposite to the firstdirection from the second end rotational position to the first endrotational position with the detectors at the second axial position. 15.The method of claim 13, wherein iteratively actuating the gantrycomprises rotating the gantry over less than a full imaging range beforeadjusting an axial position, wherein rotating the gantry over the fullimaging range corresponds to a rotation of the gantry sufficient toprovide imaging information over the gaps between the in-plane fields ofview of the imaging detectors.
 16. The method of claim 12, whereiniteratively actuating the gantry comprises axially oscillating the bedwith respect to the bore of the gantry generally continuously over aduration of an imaging scan.
 17. The method of claim 16, comprisingoscillating the bed sinusoidally with respect to time during theduration of the imaging scan.
 18. The method of claim 17, furthercomprising rotating the detectors over a first pivoting rangecorresponding to an organ of interest and a second pivoting rangecorresponding to a supplemental volume, wherein the detectors are sweptover the first pivoting range for a longer duration of time than overthe second pivoting range during performance of an imaging scan.
 19. Themethod of claim 12, wherein the first axial position corresponds to akidney and the second axial position corresponds to a bladder, furthercomprising performing a dynamic renal study using the first NM imaginginformation and the additional NM imaging information.
 20. An imagingsystem including: a first gantry having a bore therethrough; a secondgantry axially aligned with the first rotating gantry and configured tobe translatable axially relative to the first rotating gantry; a bedthat is translatable along an axis of the bore of the first gantry;plural nuclear medicine (NM) imaging detectors disposed about the boreof the first gantry and the second gantry, the imaging detectors havingan axial field of view; and a processing unit operably coupled to theimaging detectors, the processing unit configured to: axially translatethe bed and the second gantry with respect to the first gantry toposition the first gantry about a first region of interest and toposition the second gantry about a second region of interest; acquire,concurrently, NM imaging information from the imaging detectors of thefirst region of interest and the second region of interest; andreconstruct an image using the NM imaging information.